A standard power drill has a spindle that is typically rotated by an electric motor about its axis and that is threaded so that it can be fitted to a body of a drill chuck. locked at the drill spindle and clamping jaws that can be adjusted with relation to the chuck body by means of a rotatable tightening sleeve; moreover having a coupling arranged between the spindle thread and the tightening sleeve, positively locking the tightening sleeve with the spindle thread in circumferential direction when actuated.
EP 0 716 896 describes a drill having a coupling associated with a position detector that controls a switching device, switching on and off the actuation of the drill spindle in such a way that the spindle drive is switched off when the coupling is moved from the uncoupled state into the coupled state of the coupling such that the user cannot be endangered by an operating mistake when the coupling is actuated during the operation of the drill spindle. Furthermore, it is to be understood that direct access to the tightening sleeve for the actuation of the drill chuck is no longer required when the drill bit is properly chucked.